A funny timing issue occurred to me the other day. Windows apparently keeps track of USB sticks/drives you have had connected to your machine, and the drive letter they were assigned. Now let's say you had a drive mounted to Z:. If you try to mount a VeraCrypt volume on Z: while that drive is not plugged in, and you plug it in while VeraCrypt is verifying the password, the drive gets Z: and the mount fails saying the letter is already in use. I don't know if this is necessarily a bug, or a problem people are very likely to run into, but I think it is worth noting.
Comments: I confirm Enigma2Illusion statement that this is not an issue of VeraCrypt: the drive letter is not acquired by VeraCrypt until the password is verified, so if the drive letter becomes unavailable after the password verification is finished, then VeraCrypt will report the error that you received. I don't see how we can "lock" the drive letter during password verification without risking to cause other side effects. So, since VeraCrypt is actually behaving correctly and no problem are caused by this, I will close this ticket. Thank you for taking the time to report this.
Comments: I confirm Enigma2Illusion statement that this is not an issue of VeraCrypt: the drive letter is not acquired by VeraCrypt until the password is verified, so if the drive letter becomes unavailable after the password verification is finished, then VeraCrypt will report the error that you received. I don't see how we can "lock" the drive letter during password verification without risking to cause other side effects. So, since VeraCrypt is actually behaving correctly and no problem are caused by this, I will close this ticket. Thank you for taking the time to report this.